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Abstract

In this paper we present some quantitative measurements of X-ray phase contrast images and noise evaluation obtained with a recent grating based X-ray phase contrast interferometer. This device is built using a single phase grating and a large broadband X-ray source. It was calibrated using a reference sample and finally used to perform measurements of a biological fossil: a mosquito trapped in amber. As phase images, noise was evaluated from the measured interferograms.

Final reconstruction. Fig. 5(a): optical path difference (OPD) of the reference sample. Size of the reconstructed images size is (128 × 128) pixels, instead of (512 × 512) pixels for the interferograms. The resulting effective pixel size in the reconstructed images is 5.36μm. Fig. 5(b): OPD horizontal cross-section [row 80 out of the (128, 128) OPD map given in Fig. 5(a)]. The bevel height is 0.6 A.U., which corresponds to an OPD of 0.21nm as estimated from the SEM measurements. The thin green lines represent a Cartesian mapping useful to read the axes more easily. The two other thick lines are here to mark out the slope. Fig. 5(c): 20 × 20 pixels area out of the bevel, after tilt subtraction. The standard deviation in this area is equal to 2 × 10−3A.U., which corresponds to 0.7pm. It leads to a SNR of 300. We can also notice in Fig. 5(b) that the areas corresponding to the bevels are flat whereas those corresponding to the rest of the wafer are slightly non-uniform.

Application of the SPGI on a biological fossil. Fig. 6(a): reconstructed OPD of a mosquito trapped in amber. Fig. 6(b): mosquito viewed under a microscope. The red square marks out in Fig. 6(b) the area of the mosquito observed in Fig. 6(a). We can clearly observe some details of the anatomy of the mosquito in the OPD image.